This invention relates to an intake system of a V-type combustion engine, and more particularly to an intake system of a V-type engine having a surge tank above and between engine banks of the V-type engine.
An engine may comprise cylinders disposed in a straight line, opposed cylinders, or cylinders in a V-shaped form.
An intake system of the type for a V-type engine comprises, as shown in FIG. 8, first and second surge tanks 108A, 108B, first and second intake pipes 114A, 114B, and first and second fuel delivery pipes 118A, 118B. The surge tanks 108 are separated from one another, and are disposed above a space 106 defined between a first engine bank 104A (a right bank) and a second engine bank 104B (a left bank) of the V-type engine 102. The intake pipes 114A, 114B branch and extend from sides of the surge tanks 108A, 108B and intersect (i.e., cross) below the surge tanks 108, and then connect to first and second cylinder heads 110A, 110B of the engine banks 104A, 104B respectively. The fuel delivery pipes 118A, 118B are positioned in first and second spaces 116A, 116B below the surge tanks 108A, 108B and above the intake pipes 114A, 114B.
Also, another intake system of a V-type engine is divided into upper and lower block members, wherein the upper block includes a surge tank and first and second upper pipe parts of intake pipes, and the lower block includes first and second lower pipe parts of the intake pipes.
Further, such an intake system of the V-type engine is disclosed in e.g. Japanese Patent Laid-Open Official Gazette No. 62-237028, Japanese Patent Laid-Open Official Gazette No. 11-294171, and Japanese Patent Laid-Open Official Gazette No. 59-565.
The intake system disclosed in Japanese Patent Laid-Open Official Gazette No. 62-237028 has a constitution in which intake passages are connected to intake ports on the inward sides of banks of cylinder heads, and are positioned in recesses, which is formed in cylinder head covers, correspondingly to cylinder head bearings of camshafts in the other bank. Also, the intake system disclosed in Japanese Patent Laid-Open Official Gazette No. 11-294171 has volume chambers and resonance passage parts formed integrally in a collector. Further, the intake system disclosed in Japanese Patent Laid-Open Official Gazette No. 59-565 includes a supercharge high pressure pipe type intake manifold which is arranged in a relatively wide space between cylinders of the V-type engine. A space for adjacent outer engine elements is secured to permit smaller composition.
However, the conventional intake system of the V-type engine has inconvenience when the intake system is divided into an upper block which includes the surge tank and the upper pipe parts of the intake pipes, and a lower block, which includes the lower pipe parts of the intake pipes. That is, seal parts of the intake pipes enter inwardly into the surge tank, and therefore coupling bolts for coupling the upper and lower blocks are also required on the inner side of the surge tank to provide sealability of the intake pipes. This requirement results in complicated constitution of the system, difficulty of assembly of delivery pipes, and a heavier system.
In order to obviate the above inconveniences, the present invention provides an intake system of a V-type engine having a surge tank above and between first and second engine banks of the V-type engine. First and second intake pipes form therein first and second intake passages, and branch and extend from both sides of the surge tank to cross below the surge tank to connect to the engine banks. In first and second spaces which are defined by a lower part of the surge tank and upper parts of the intake pipes, first and second delivery pipes are disposed. An intake system structure is formed by the surge tank and the intake pipes. The intake system structure is divided into upper and lower blocks by a horizontal dividing surface positioned below the surge tank. The upper block includes the surge tank, and first and second upper pipe parts of the intake pipes. The lower block includes first and second lower pipe parts of the intake pipes. First and second seal parts surround the intake passages on the dividing surface toward the upper block. First and second straight inner sealing surfaces are arranged at the portion where the seal parts extend internally toward the engine banks. Only these straight inner sealing surfaces are positioned below the surge tank.
According to the present invention, the intake system structure is thus divided into upper and lower blocks, so that installation of fuel delivery pipes below the surge tank can be made easier. Also, the inner seal parts of the intake pipes are formed to be straight, and only these parts are positioned below the surge tank, so that the seal parts on the dividing surface of the intake pipes do not protrude inwardly toward the surge tank. Accordingly, the sealability of the intake pipes can be achieved without coupling bolts on the inner side of the surge tank, which permits easier composition and a lighter system.